A positive clutch also called “dog clutch” or “jaw clutch” is used in reduction gears. The positive clutch is a power transmission mechanism of the type wherein protruding parts provided on one of a driving-side rotating body and a driven-side rotating body are brought into meshing engagement with recessed parts provided in the other of the driving-side rotating body and the driven-side rotating body while the driving-side rotating body is rotating so that a driving force is transmitted from the driving-side rotating body to the driven-side rotating body. As to the shape and configuration of the protruding parts and recessed parts, various proposals have been made as disclosed, for example, in Patent Document 1. FIG. 16 hereof shows a dog clutch disclosed in Patent Document 1.
As shown in FIG. 16, a recessed part 101 is engaged with a protruding part 102. The protruding part 102 is formed on a driving-side rotating body 103 and the recessed part 101 is formed in a driven-side rotating body 104. In this instance, when the driving-side rotating body 103 is rotating in a direction of arrow X, a side surface 105 of the protruding part 102 comes into abutment with a torque-receiving surface 106 of the recessed part 101 and, subsequently, the driven-side rotating body 104 is rotated in the direction of arrow X. Alternatively, when the driving-side rotating body 103 is rotating in a direction of arrow Y, a side surface 107 of the protruding part 102 comes into abutment with a torque-receiving surface 108 of the recessed part 101 and, subsequently, the driven-side rotating body 104 is rotated in the direction of arrow Y.
Patent Document 1 has no disclosure about a method of producing the recessed part 101 of the dog clutch, however, the recessed part is normally formed by cutting. A cutting method will be briefly described with reference to FIG. 17.
As shown in FIG. 17(a), a blank material or workpiece 109 is provided. The workpiece 109 is subjected to a cutting process using an end mill or a milling cutter so as to form a recessed part 101 shown in FIG. 17(b). In FIG. 17(b), a symbol “∇” is a finish symbol used to indicate a texture of machined surface.
The cutting process involves generation of a great amount of chips. Cutting time and machining man-hours increase as the amount of chips increases. Furthermore, generation of a huge amount of chips leads to wasteful consumption of material. A demand for a reduction in the production cost requires reductions of the cutting time and the amount of chips generated.